Dynamics of cavitation bubbles generated by multi-pulse laser irradiation of a solid target in water

The effect of the second and later pulses on the expansion dynamics of the cavitation bubble produced by multi-pulse microchip laser irradiation of a Cu target in water has been investigated. We clarified the bubble dynamics by taking shadowgraph images and measuring the bubble radius as a function of time. Shock waves were also measured to investigate the explosive expansion of the bubble. As a result, the second and later pulses did not cause an explosive expansion, and the ablation of the target by these pulses was rather mild, although they had a certain contribution to the expansion of the bubble. The energies given to the bubble expansion from the first pulse and also from the second pulse were estimated by comparing the experimental results with the calculation based on the Rayleigh model.     

Host–Guest Complexation Behavior of Resorcinarenes with Tetraalkylammonium Ions and N-Methylpyridinium Ions in Methanol: The Effect of Bulky Hydrophobic Substituents at the Extra-Annular Positions

The host–guest interaction of C-methylresorcin[4]arene and its derivative having four tert-butylsulfanylmethyl groups at the extra-annular positions was studied by ¹ H NMR spectroscopy in CD₃OD. Based on the association constants (Ka) and the complexation-induced NMR shifts (CIS), it was concluded that the bulky substituents create a deep cavity with a narrow entrance and improve the size and shape selectivity.     

Phase-transfer-mediated electrochemical reaction: anodic disulfide bond formation under biphasic condition

The use of bromide ion as a redox mediator promotes electrochemical reactions in the non-conductive cyclohexane phase. Anodically oxidized species of bromide ion in the conductive methanol phase can bring oxidizing power across phases to induce oxidative disulfide bond formation of a hydrophobically-tagged tripeptide, which is located predominantly in the cyclohexane phase. In addition to commonly used tetraalkylammonium salts, inorganic sodium salt can also be effective alternatives for the bromide source.     

Aggregation behavior of poly(γ‐benzyl‐L‐glutamate)‐b‐polyisoprene‐b‐poly(γ‐benzyl‐L‐glutamate) rod‐coil‐rod triblock copolymer in N,N‐dimethylformamide

Solution property of poly(γ‐benzyl‐L ‐glutamate)‐b‐polyisoprene‐b‐poly(γ‐benzyl‐L ‐glutamate) (GIG copolymer) was studied by using dynamic light scattering and static light scattering for N,N‐dimethylformamide (DMF) solution and DMF/toluene mixed solutions. GIG copolymer proved to aggregate in DMF and under DMF‐rich condition, that is, high‐polar region. The aggregate decreased in size, and completely disappeared under toluene‐rich condition, that is, low‐polar region. The correlation between solubility parameter and aggregate size of GIG copolymer in the DMF/toluene solution systems quantitatively demonstrated how strongly polarity caused by hydrogen bond made an impact on the aggregation behavior. Because the main driving force to the aggregation under DMF‐rich condition originates with polyisoprene (PIP) blocks, the aggregate in DMF is considered to be a core‐shell micelle consisting of flexible PIP core surrounded by rigid poly(γ‐benzyl‐L ‐glutamate) (PBLG) shell. The values of dimensionless parameter ρ, defined as the ratio of radius of gyration 〈S²〉^1/2 to hydrodynamic radius R_H, revealed that a single chain of GIG copolymer had the form of rigid rod with flexibility, that is, once‐broken rod, caused by the incorporation of a flexible PIP chain between two rigid PBLG rods in the DMF/toluene solution system. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1740–1748, 2010     

Solution to the boundary blowup problem for k-curvature equation

We consider the boundary blowup problem for k-curvature equation, i.e., H _k [u] = f(u) g(|Du|) in an n-dimensional domain Ω, with the boundary condition u(x) → ∞ as dist (x,∂Ω) → 0. We prove the existence result under some hypotheses. We also establish the asymptotic behavior of a solution near the boundary ∂Ω. Mathematics Subject Classification (2000) 35J65, 35B40, 53C21